Hydraulic steering mechanism



Jan. 23, 1951 G. w. HARDY HYDRAULIC STEERING MECHANISM 3 Sheets-Sheet 1 Filed Jan. 6, 1945 INVENTOR Gonoou W. HARDY BY ATTORNEY Jan, 23, 1951 G. w; HARDY HYDRAULIC STEERING MECHANISM 2 t e e h s A. t e e h S 3 E N o 5 M H 0 N 6 m mm mm on 3 2 g J d e l a i F INVENTOR GORDON W HARDV -A ,WM ATTORNEY Jan. 23, 1951 G. w. HARDY HYDRAULIC STEERING MECHANISM 3 Sheets-Sheet 5 Filed Jan. 6, 1945 4 V M mm mm I 6% a TH. N m m J L ""55 W N c u l O D A m Gm Patented Jan. 23, 1951 Y UNITED "STATES PATENT, OFFICE Application Jamale, 1945, Serial No. 571,571

3 Claims. 1

The present invention relates to a fluid actuated mechanism to shift a member with respect vto its supporting frame and more particularly to a steering mechanism in which the member is a vehicle wheel mounted to be shifted or turned on its supporting axle.

As the size of vehicles has increased their wheels and the loads placed on them have also increased to a point where it is necessary to pro vide means to increase the turning force which can be applied by the human operators to turn the wheels. Such mechanisms are not broadly new but have heretofore been subject to certain disadvantages and open to improvement. One form of such mechanism has employed two piston-cylinder units, one at the wheel and one at the steering position, to transmit the turning force by fluid pressure to the former from the latter. This invention is concerned with an improved type of such gear.

The general object of the present invention has been to provide an improved steerin mechanism employing a fluid operated servo system to receive the turning thrust from the operator, multiply it and then transmit it to the wheel or wheels to be turned. A further object of the invention has been to provide such a mechanism in which the wheel, after turning, may be returned to its original position by reversing the action of the system. Still another object of the invention has been to provide means for applying the turning force to the wheel in a plurality of increments by employing a servo system at the time turning is begun and, it the wheels resistance is too great, automatically applying the force of a booster system to supplement the servo system. A still further object of the invention has been to provide a servo cylinder and piston unit and a booster cylinder and piston unit mounted adjacent the vehicle axle and preferably in alignment therewith and connected with the wheels to turn them as force is applied from the steering wheel. An additional object has been to provide a more positive, less expensive and more simple construction than heretofore has been available.

Other objects of the invention will become apparent from study of the specification and the attached drawings in which:

Fig. 1 is a schematic layout of the entire mechanism of the invention;

Figs. 2 and 3 are alternate forms of servo and booster cylinder units;

Fig. 4 is a cross section of the master cylinder unit;

Fig. 5 is a cross section through the master cylinder replenishing pump; and,

Fig. 6 is a section through a booster operating valve.

Referring generally to parts which later will be described in detail the mechanism consists of two cylinder and piston units, a master unit at the steering wheel and a servo unit, supplemented by a booster unit, at the axle of the wheels to be turned. Fluid lines connect each end of the master cylinder with each end respectively of the servo unit cylinder. Fluid, preferably oil, fills the chambers formed in the two cylinders by the pistons and also the connecting lines.

Rotation of the steering wheel shifts the master cylinder and piston with respect to each other to increase the fluid pressure in one chamber and decrease it in the other, thus effecting a pressure differential between opposite sides of the master piston. This difierential is transmitted through the lines to the servocylinder to shift the piston in it. Since this latter piston is connected to the vehicle wheel, the wheel is turned. When the master piston is returned to its initial position the wheel is likewise returned. No fluid is expended from the system during an operating cycle.

If the resistance to turning oifered by the wheel is too great and exceeds a predetermined amount the pressure in the line connected with the chamber subject to pressure rise will increase until it is high enough to open a spring loaded valve. This valve normally closes a line between a source of fluid under pressure, air oroil, and the cylinder of a booster unit consisting of a cylinder and piston. The booster piston is thus moved and as it too is connected to the wheel it supplements the servo unit in shifting it to the desired angle to the vehicle airle.

The booster unit may comprise one piston with two piston rods, one connected to each wheel; or two pistons with each piston connected to only one wheel. In either case the attainment of a predetermined pressure in one master cylinder fluid line will actuate booster action in one direction while the attainment of a predetermined pressure in the other master cylinder'line will actuate the booster in the opposite sense. If oil is used to actuate the booster it may be supplied at the desired pressure by a pump and after use returned through an oil sump. If air is used it may be supplied by an air storage tank or accumulator and after use exhausted to the atmosphere. v

3 inegeneraideseripticngivenshovewmnow thedrawimaparnectedtoasteering wheel I3 rotatablymounted on the vehicle trams. notation the wheel operstesmechanismhereaiterdesa'ibedtoshii't the'plston carriedinthemsstercyilnder.

Remoteiromthesteeringwheelisaeylinder blockllsecuredbyboitstothevehicietrontaxle I3. Thisisachanneishapedmemberandthe blockllisp ovidedwithbosseshbearing against the web or the channel. This cylinder blockisiormedtoprovide cylinders iortheservo andbooster pistons. ThecyiindersmaybearrangedasshowninFig.2orFIg.3orthecylln-' ders may be separated the one from the other. although they shouldpreterably be maintained parallel with the axis oi their supporting axle. The block I5 may be formed in any desired manner although preferably this will be a casting.

Fluid supply lines 33 and 33 connect with opposite ends or the master cylinder II at 31 and 33 and with opposite ends or the servo cylinder at 33 and 3i respectively. Provision is made thro ah Ta 33' and 33 in lines 33 and 33 to actuate valves 35 and 35 controlling the booster operation in a manner herearter to be described.

'l'o nlltne master cylinder, the servo cylinder and their connecting lines; oil is forced into the enus oi the master cylinder through lines 31 and 33. The lines may be supplied by a combination of a filling tank or pump 33 (Fig. 5) and two manually operated piston pumps 33 and 33 operating in cylinders 35 and 33 and receiving oil through ports 33 from the tank 30 in which the cylinders are located. Aiternatively the master cylinder I0 may be supplied through lines 31 and 33 from an oil line supp ying oil at a pressure of approximately 40 pounds per square inch game. This oil may be supplied from the vehicle lubricating system. To permit release of air from the system when it is filled vents 33 in the block leading to the servo cylinder are removed and later replaced.

As the master piston is shifted in its cylinder I0 the pressure on one side of the servo piston (Fig. 2) will be increased and on the other side decreased. The servo piston will move in the direction or least pressure and through its piston rods 53 and 53 pull on one wheel and push on the other to turn them. Connection to each wheel from a respective servo piston rod is made through a knuckle 55, universal connection 51 and tie rod 53 to'a cross arm 00, all shown diagrammatically. The piston rods are secured to respective cross arms.

The details of construction oi the servo and booster piston and cylinders are shown in Figs. 2 and 3. The block I5 is shown in Fig. 2 to consist of three cylinders. The servo cylinder, indicated at 33, extends from end to end and is closed by threaded caps 53 bored to receive piston rods 53 and53. The outer ends of'the piston rods are formed with a shoulder and a threaded portion of reduced diameter. This portion passes through a hole in cross arm 30 and the shoulder is drawn tightly against the tie rod by bolts 65.

Oil for shifting the piston 50 is admitted at the ends 01' the servo cylinder through fittings 33 and 3| communicating with lines 33 and 33 respectively (Fig. 1). To prevent leakage of oil irom one side of the piston 53 to the other a plurality oi annular recuses 31 are cut therein to 3 receiveasynthetlcmbberrlngandrormalinear seaibetweentnepistonandtne cylinder sidewall. These rings are indicated at as and are incor- 'rectlysnovvnasncuonedtoemphaslsetheirpositiou. eimnarseaissreiormedintheendcsps ntopreventleasagewherethepistonrodspsss 3113011831 them.

'lwoalignedboostercylindersllandll are formed in the block II in the construction of Pig. 3. They are parallel with the servo cylinder 33 and are separated from each other by a cylinder e d wall 13. These cylinders also are closed with end caps 33 bored to receive piston rods -l5 and 13 secured to pistons l3 and 13 respectively. The other ends of the piston rods are secured to respectivecrossarmslsinthesamemannerasare servo piston rods 53 and 53. To protect the extended ends of the piston rods a wrrugated boot 30 is provided at each end of block I5 to form a resilient covering extending between that end and the adjacent cross arm.

The construction of Fig. 3, which has the advantage of being shorter than that of Fig. 2 in comparable installations, employs a single booster cylinder like its associated servo cylinder. The cylinder indicated at 30 carries a single piston 33 provided with opposed piston rods 33 and 33 connected through end caps 33 to respective cross arms 60. In all other respects than those mentioned above this alternative construction is like that shown in'Flg. 2.

Fluid to actuate the booster pistons is supplied to the cylinders through fittings I00 and I03 to which are connected lines I33 and I05. These lines lead to valves 35 and 33 respectively. The construction of these values is shown in cross section in Fig. 6. Twoother lines enter each valve; one from an oil pump or air storage tank, depending on whether liquid or gas is used to shift the booster piston. Another line leads from each valve to an oil sump or exhaust to atmos phere, again depending on what fluid is used. The pump or tank is indicated at I03 and the sump or exhaust at IIO.

A line H3 passes from supply unit I03 to a T II3 where it divides into lines H5 and III leading to valves 35 and 35 respectively. In like manner lines III and Ill exhaust from valves 35 and 35 to a common line II3 leading to ill.

Each valve (Fig. 6) is provided with a dumbbell piston I30 each end of which is closely fitted to cylinder sidewall I33 to provide a fluid-tight seal therewith. The piston is normally held in the exhaust position (lines I03 and II! or I35 and I I3 in communication) by a calibrated spring I35. The force this spring exerts on the piston I30 is governed by an adjustment I3l threaded into the valve case.

To enable a predetermined pressure in line 33 or 33 to actuate valve 35 or 30 a short line leads from T 33 or 33 to communicate with a calibrated orifice I30 in the valve case (Fig. 6). When this predetermined pressure is reached in either line the resistance of spring I35 in the associated valve is overcome and piston I30 is moved up to place lines H5 and I03 or H6 and I05, as the case may be, in communication.

This permits fluid under pressure to fiow through the indicated fitting I00 or I03 and actuate the booster mechanism to supplement the thrust of the servo system. It the construction oi. Fig. 2 is employed either piston 18 or 13 will act through piston rod I5 or 16 to push on the same tie rod against which the force of the servo piston 50 is already being exerted. In like manner, it the construction of Fig. 3 is used the piston 92 will exert its force in the same direction as servo piston 50. In this connection it should be noted that the relative positions of fittings I and I02 are reversed in Fig. 3 as compared with Fig. 2.

The fact that the booster mechanism is operating in one direction as by admission of fluid at I00 requires that fluid simultaneously be exhai'sted from the block at I02 due to the motion of the steering gear. This is possible because if valve 35 is positioned to admit fluid to the block at I00 the valve 36 connected to fitting I02 remains in the exhaust position. This is due to the fact that as pressure is built up in one line 22 or 24 it is relieved in the other and thus the latters associated valve remains at exhaust due to spring I25.

Reference should be made to the construction of master cylinder I0 and its components to see how pressure is simultaneously built up in one of lines 22 or 24 and relieved in the other, accompanied by displacement of oil in the servo system itself.

This master cylinder comprises a cylindrical portion I3I to which are secured by suitable bolts, end caps I32 and I33. The cap I33 is provided with an axial extension I35 of reduced diameter terminating in an external thread I36. An internall-y threaded cover I38 is secured to threads I36 and carries one race of a ball thrust bearing I39. The other race is carried by the steering column I40 and bears against a, thrust collar I42 thereon. Lubricant may be supplied to said cover through an opening normally closed by a grease plug 3. 7

Thrust at the end of the steering column is received by a single ball thrust bearing consisting of a ball I45 received in a semi-spherical socket at the end of the column and one in the end of a plug I41. This plug is threadingly received in the bore of a hollow extension I48 of the end cap I32. The tightness of the column between-the two thrust bearings may be regulated by rotation of the plug I 41.

A master cylinder piston I50 is mounted for reciprocation but restrained against turning in the master cylinder. This piston is provided with two hollow extensions I52 and I54 which are formed to have a sliding fit with the inside of caps I32 and I33. Linear seal I55 and I56 insure that there shall be no leakage of oil from the master cylinder to the steering column. Similar seals are provided between the piston and cylinder sidewall.

The piston is reciprocated in the cylinder by rotation of the steering column I40. To this end the column is threaded as at I58 to engage a complementary thread in the piston I50. Also, the piston is restrained against rotation by two or more keys I60 carried in the extension I35 and riding in slotted keyways I62 in the piston extension I54. The keys are kept in looking relation to the extensions I35 and I54 by the steering post but do not pass through or into the post. Thus as the steering wheel is turned, the piston will be moved in one or the other direction in its cylinder. A passage I64 in the column I40 permits flow of lubricant from one side of the piston thread to the other and prevents any locking of the piston by entrapment of steering column lubricant.

Movement of the piston in one direction increases the pressure on the oil inone piston-cylinder chamber and relieves it in the other. If the pressure on the oil in the upper chamber (Fig. 4) is increased it will force 011 through line 22 to operate the servo piston and turn the wheels. At the same time the movement of the piston upwardly will increase the volume of the lower chamber and permit, in fact assist by suction, transfer of oil from the servo cylinder fed by line 24 back into the chamber. Movement of piston I in the opposite direction will transfer oil out of the lower chamber and draw it into the upper chamber to move the wheels in the opposite direction. The operation of the booster system also is controlled by movement of piston I50. As it builds up pressure in either line 22 or 24 to a predetermined value against the resistance to turning offered by the road wheels eitner valve 35 or 36 .will be operated to permit the corresponding booster to supplement the servo piston. The turning force on the road wheels by the booster continues only so long as the driver continues to exert suflicient force on the steering wheel to cause pressure in the line 22 or 24 to move the valve I20 against the valve return spring I25 suiiicient to maintain the lines I04 and H5 or I05 and H6 in communication. Thus the angle of turning of the road wheels is determined primarily or is always fully controlled by the amount the steering wheel is turned manually. Thus the booster can never overrun the turning effect on the road wheels by the steering wheel and can never come into play until steering requires more than a certain determinable application of force.

It will be seen that no oil is expended in the servo system as the master piston is operated. Oil is merely transferred to or from the servo and master cylinders.

From time to time it is necessary, due to leak- .age, to replenish some of the oil in the system.

This is done by removing the cover to the pump 40 and manually operating the piston 42 and 44. Flow of oil back to the pump is prevented by check valves I10 (Fig. 5). If the vehicle lube system is used its pressure will force oil into the cylinder I0 to charge the servo system. As heretofore stated, the vents 49 in the servo cylinder should first be opened to release air trapped in the system.

From the foregoing description it will be seen that I have provided a novel steering mechanism comprising a servo system and a booster system. Both are controlled from the steering wheel. The servo system is operated by rotation of the steering wheel and the booster system, already conditioned for use, is set in operation when rotation of the steering wheel results in abnormal pressure in either line 22 or 24.

I claim:

1. In a fluid actuated device, a fluid pressure means, a fluid conductor tube communicating therewith, an actuated piston, an enclosed cylin der for said actuated piston with which said fluid conductor communicates, a booster piston connected with said actuated piston, an enclosed cylinder confining said booster piston, a second fluid pressure means, a valve device having an inlet port, an exhaust port, a movable valve element, and a pair of ports controlled by said valve element, one of said pair of ports being. in normal position of said valve element, open to said exhaust port, means connecting said fluid conductor tube with the inlet port of said valve device, said one of the pair of ports communicatin: with said booster piston and the other of 7 said pair of ports communicating with said second-mentioned fluid pressure means, said valve element, at a predetermined pressure within said fluid conductor tube, adapted to be moved to inlet port, an exhaust port, a movable valve element, and a pair oi ports controlled by said valve element, one of said pair of ports being, in normal position of said valve element, open to said exhaust port, means connecting said fluid conductor tube with the inlet port of said valve device, said one of the pair of ports communicating with said booster piston and the other of said pair of ports communicating with said secondmentioned fluid pressure means, said valve element, at a predetermined pressure within said fluid conductor tube, adapted to be moved toclose the one of said pair of ports from the exhaust port and to connect the pair of ports together, whereby the second fluid pressure supply communicates with said booster piston to actuate the same, said valve device including a spring tending to hold said valve element in said normal position against pressure in said fluid conductor tube.

3. In a fluid actuated device, a fluid pressure means, a fluid conductor tube communicating therewith, an actuated piston, an enclosed cylinder for said actuated piston with which said fluid conductor communicates, a booster piston connected with said actuated piston, an enclosed 8 cylinder confining said booster piston. a second fluid pressure means, a valve devicehaving an inlet port, an exhaust port, a movable valve element, and a pair of ports controlled by said valve element, one of said pair of ports being, in normal position oi! said valve element, open to said exhaust port, means connecting said fluid conductor tube with the inlet port of said valve device. said one of the pair of ports communieating with said booster piston and the other of, said pair 01' ports communicating with said sec-i end-mentioned fluid pressure means, said valve element, at a predetermined pressure within said fluid conductor tube, adapted to be moved to close the one of said pair of ports from the exhaust port and to connect the pair of ports together, whereby the second fluid pressure supply communicates with said booster piston to actuate the same. said exhaust port having a tube connected therewith and a sump into which said tube extends.

GORDON W. HARDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

